docs: def read_discrete_inputs(slave_id, starting_address, quantity):
      """ Return ADU for Modbus function code 02: Read Discrete Inputs.
  
      :param slave_id: Number of slave.
      :return: Byte array with ADU.
      """
      function = ReadDiscreteInputs()
      function.starting_address = starting_address
      function.quantity = quantity
  
      return _create_request_adu(slave_id, function.request_pdu)